From 1faffa048640c97b96b77118acb1359c92f970c9 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Thu, 27 Feb 2025 15:04:57 +0000
Subject: [PATCH] gh-130618: Fix parser error when using lambdas inside
 f-strings

---
 Lib/test/test_grammar.py                             | 12 ++++++++++++
 .../2025-02-27-15-07-06.gh-issue-130618.JTcsRB.rst   |  3 +++
 Parser/lexer/lexer.c                                 |  6 +++++-
 3 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2025-02-27-15-07-06.gh-issue-130618.JTcsRB.rst

diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index 6a841587f49166..994c8a0e15ac40 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -1972,6 +1972,18 @@ async def foo():
         with self.assertRaises(Done):
             foo().send(None)
 
+    def test_complex_lambda(self):
+        def test1(foo, bar):
+            return ""
+
+        def test2():
+            return f"{test1(
+                foo=lambda: '、、、、、、、、、、、、、、、、、',
+                bar=lambda: 'abcdefghijklmnopqrstuvwxyz 123456789 123456789',
+            )}"
+
+        self.assertEqual(test2(), "")
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-02-27-15-07-06.gh-issue-130618.JTcsRB.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-27-15-07-06.gh-issue-130618.JTcsRB.rst
new file mode 100644
index 00000000000000..de67496108e2a7
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-27-15-07-06.gh-issue-130618.JTcsRB.rst
@@ -0,0 +1,3 @@
+Fix a bug that was causing ``UnicodeDecodeError`` or ``SystemError`` to be
+raised when using f-strings with ``lambda`` expressions with non-ASCII
+characters. Patch by Pablo Galindo
diff --git a/Parser/lexer/lexer.c b/Parser/lexer/lexer.c
index 8c5ae37fa90860..207fb6b363766c 100644
--- a/Parser/lexer/lexer.c
+++ b/Parser/lexer/lexer.c
@@ -211,9 +211,13 @@ _PyLexer_update_fstring_expr(struct tok_state *tok, char cur)
             break;
         case '}':
         case '!':
-        case ':':
             tok_mode->last_expr_end = strlen(tok->start);
             break;
+        case ':':
+            if (tok_mode->last_expr_end == -1) {
+               tok_mode->last_expr_end = strlen(tok->start);
+            }
+            break;
         default:
             Py_UNREACHABLE();
     }